Numerical Simulation of Back Spatter and Weld Pool Dynamics in Laser Welding of 430 Ferritic Stainless-steel Thin Plate

GAO Tian; ZHAO Pengcheng; YAN Guoshuai; WANG Ziqiang; JING Shuixiu; ZHAO Zhenhui; LIU Jun

doi:10.7512/j.issn.1001-2303.2024.08.16

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Numerical Simulation of Back Spatter and Weld Pool Dynamics in Laser Welding of 430 Ferritic Stainless-steel Thin Plate
Vol. 54, Issue 8, Pages: 118-127(2024)
Received：31 January 2024，

Revised：2024-04-03，

Published：25 August 2024
DOI： 10.7512/j.issn.1001-2303.2024.08.16
稿件说明：

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高天，赵朋成，燕国帅，等.430铁素体不锈钢薄板激光焊接背面飞溅和熔池动态的数值模拟［J］.电焊机，2024，54（8）：118-127. DOI： 10.7512/j.issn.1001-2303.2024.08.16.

GAO Tian, ZHAO Pengcheng, YAN Guoshuai, et al.Numerical simulation of back spatter and weld pool dynamics in laser welding of 430 ferritic stainless-steel thin plate[J].Electric Welding Machine, 2024, 54(8): 118-127. DOI： 10.7512/j.issn.1001-2303.2024.08.16.

摘要

薄板的激光焊接对离焦量敏感，很小的离焦量偏差就会导致熔池不稳定。本文采用数值模拟的方法，研究了离焦量对0.6 mm厚430铁素体不锈钢薄板激光焊熔池动态行为的影响，分析了形成焊道背面飞溅的原因。结果表明，在目前所用的焊接工艺参数条件下，离焦量决定着激光热输入在熔池中的位置和分布。熔池中匙孔的深度随着离焦量的降低而增大，负离焦（-0.1 mm）形成穿透的匙孔，零离焦（0 mm）和正离焦（+0.1 mm）形成的匙孔尺寸较小。不同离焦量均形成具有束腰结构的熔透熔池，熔池表面和匙孔表面的流速最大。熔池高度方向上存在由中间束腰部位向上下表面流动的两个涡流，液体金属在熔池上表面由熔池后方向前方流动。匙孔中的蒸发作用力和表面的高流速使匙孔不断闭合，在底部形成封闭的气泡。背面飞溅只在负离焦条件下形成，零离焦和正离焦不产生背面飞溅。负离焦条件下，熔透熔池形成的初期在焊道背面形成小颗粒的滴落型飞溅，主要是由熔池重力和表面流动导致；在穿透匙孔形成的末期因为气泡破裂形成大颗粒的喷射型飞溅。正离焦条件下熔池的形态、流动较为稳定，预测的焊道横断面轮廓与实验结果吻合良好。

Abstract

Since a small deviation in the off-focus value can lead to an unstable weld pool

the laser welding of thin plates is highly susceptible to this parameter. Based on numerical simulation

effects of off-focus on the dynamic behaviors of the weld pool in laser welding of 430 ferritic stainless-steel plates in 0.6mm thick were investigated. The reasons behind the formation of spatters on the back of the weld bead were examined. The results show that the position and distribution of laser heat input in the weld pool are primarily determined by the off-focus. As the off-focus value decreases

the keyhole in the weld pool gets deeper. A negative off-focus (-0.1 mm) creates a fully penetrated keyhole

while zero (0 mm) and positive (0.01 mm) off-focus creates smaller keyholes. All off-focuses form weld pools with a same waist structure

and the maximum flow velocities are observed on the surfaces of the weld pool and keyhole. Two eddy currents flowing from the middle waist to the upper and lower surfaces exist in the weld pool

and the molten metal on the upper surface of the weld pool flows forward from its rear to its front. Due to the evaporation force and high surface flow velocity

the keyhole continuously seals off in its middle

leading to closed bubbles at the bottom. Only negative off-focus causes back spatter

while zero and positive off-focus do not cause it. In the case of negative off-focus

small droplet spatters form on the back of the weld during the initial formation of the weld pool

chiefly caused by the gravity and surface flow. Jet spatters resembling large particles are formed due to bubble rupture during the final stage of the formation of the penetrated keyhole. There is a relatively stable shape and flow of the weld pool in the case of positive off-focus

and the predicted profile of the weld bead on the cross-section is in good agreement with the experimental results.

关键词

Keywords

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